Cell Signaling Flashcards

Flashcards covering key vocabulary and concepts from the Cell Signaling lecture notes.

Signal transduction

A process by which an extracellular signal produces a change in the intracellular state of the target cell and ultimately evokes a response of the target cell

Receptor

Molecule that binds the signal with high affinity

Second messengers

Small molecules that rapidly diffuse the signal inside the cell

Water-soluble second messengers

cAMP, cGMP, Ca2+, IP3

Lipid-soluble second messengers

DAG and PIP3

How intracellular signals are transmitted

Binding to another signaling molecule, Binding to a second messenger, Covalent modifications (phosphorylation, ubiquitylation or other), Binding to GTP/GDP

Types of Signaling Molecules

Small molecules like amino acids and derivatives, Gas, Steroids, derivatives of cholesterol, Eicosanoids, derivatives of arachidonic acid, Polypeptides and proteins

Surface receptors

Coupled to ion channels, Coupled to G proteins, Coupled to enzymes (e.g. tyrosine kinases)

Intracellular receptors

Coupled to transcriptional factors (nuclear receptors), Coupled to enzymes (e.g. guanylyl cyclase)

Surface receptors coupled to ion channels

Ligand-gated channels rapidly convert an extracellular signal into an electrical signal

G protein-coupled receptors (GPCRs)

The largest family of cell surface receptors

GEF

Guanine nucleotide Exchange Factors

GAP

GTPase Activating Protein

αs G protein

Stimulate adenylyl cyclase ↑cAMP

αi/o G protein

Inhibit adenylyl cyclase ↓cAMP

αq/11 G protein

Activate Phospholipase β ↑DAG & Ca2+

α12/13 G protein

Activate Rho-GTPases

βγ G protein

Activate PI3-kinase: ↑PIP3; Also opens K+ channels in heart

cAMP

Effects are mediated by cAMP-dependent protein kinase, or protein kinase A (PKA)

Cellular Adaptation to Signals

Cells can adjust their sensitivity to a signal via receptor sequestration, receptor down-regulation, receptor inactivation, inactivation of signaling protein, and production of inhibitory protein

Agonist

A substance that upon binding to the receptor mimics the action of the ligand

Antagonist

A substance that upon binding to the receptor dampens or blocks the ligand-mediated response.

Phospholipase C (PLC)

Catalyzes the hydrolysis of PIP2 in DAG and IP3

Ca2+ signaling

Increases of cytosolic Ca2+ concentrations evoke many cellular responses through the binding Ca2+-regulated proteins

PIP3

Phosphatidylinositol 3,4,5-trisphosphate evokes signal by targeting proteins containing the pleckstrin homology (PH) domain to the plasma membrane